The thermoacidophile, Sulfolobus acidocaldarius, lacks peptidoglycan, but still possesses a cell wall. What is likely to be true of this species? 1.It is a bacterium. 2.It is an archaean. 3.The optimal pH of its enzymes will lie above pH 7. 4.The optimal pH of its enzymes will lie below pH 7. 5.It could inhabit certain hydrothermal springs. 6.It could inhabit alkaline hot springs.